Changes in ventriculoatrial intervals with bundle branch block aberration during reciprocating tachycardia in patients with accessory atrioventricular pathways.

During reciprocating tachycardia in patients with accessory atrioventricular pathways, the observation of changes in ventriculoatrial (VA) intervals with bundle branch block (BBB) aberration has been used to localize the site of the pathway and prove the participation of the pathway in the tachycardia. In this report we present the changes observed during BBB in 93 patients with single atrioventricular pathways in whom the site of their pathways was subsequently proved at the time of their surgical interruption. In patients with left or right free wall pathways, the minimum VA interval (VA min) increased by 61 +/- 19 msec with ipsilateral BBB, whereas no change occurred with contralateral BBB. The smallest increase in the VA interval was 35 msec. In 14 patients, shortening of the AH intervals resulted in changes in overall cycle length that were less than 35 msec. Patients with septal pathways all had changes in VA min of 25 msec or less with either right or left bundle branch block (RBBB or LBBB), which ...